Quick install

Graphical way

Search for vlc and install it.
You may also want to install browser-plugin-vlc.

If you are interested in streaming or transcoding,
you should additionnally install libavcodec-extra-53.

Command line way

% sudo apt-get update
% sudo apt-get install vlc browser-plugin-vlc

Nota Bene

Ubuntu includes whichever VLC version was the latest
at the time the Ubuntu release was frozen
(typically about two months before the official Ubuntu upgrade).
Afterward, you can still get security and critical bug fixes,
but no further major VLC version updates until the next Ubuntu release.

If you need a more recent version, please consider upgrading Ubuntu.

Playing DVD (libdvdcss)

In order to be able to play region-locked DVD, you need install libdvdcss2.
You should follow this procedure
to install libdvdcss2.